Perjanjian itu berlaku selama satu tahun.

Itu is a demonstrative word meaning that, and in many contexts it can also function like the when the thing is already known from context.

So:

• perjanjian itu = that agreement / the agreement

In Indonesian, words like ini and itu usually come after the noun:

• rumah itu = that house
• buku ini = this book
• perjanjian itu = that/the agreement

This is normal Indonesian word order.

It can mean either, depending on context.

Indonesian does not have articles exactly like English the and a. Because of that, itu often does double duty:

• literally: that agreement
• naturally in context: the agreement

If the speaker is referring to a specific agreement already known in the conversation, English will often translate it as the agreement.

Berlaku is a very common word meaning things like:

• to be valid
• to be in effect
• to apply
• to be operative

In the sentence Perjanjian itu berlaku selama satu tahun, the most natural meaning is:

• the agreement is valid
• the agreement remains in effect

So berlaku is a good word for contracts, rules, laws, tickets, permits, and similar things.

Examples:

• Tiket ini berlaku sampai besok. = This ticket is valid until tomorrow.
• Aturan itu berlaku untuk semua orang. = That rule applies to everyone.

Indonesian often does not use a separate verb like English to be in the same way.

In this sentence, berlaku already functions as the main predicate, so there is no need for is.

Word-for-word structure:

• Perjanjian itu = the agreement
• berlaku = is valid / applies
• selama satu tahun = for one year

So the sentence is complete without any separate word for is.

Here selama means for in the sense of for a duration of time.

So:

• selama satu tahun = for one year

It can also mean during, depending on context.

Examples:

• Saya tinggal di sana selama dua bulan. = I lived there there for two months.
• Selama liburan, kami di rumah. = During the holiday, we were at home.

In your sentence, it clearly indicates duration.

Satu tahun literally means one year.

In English, one year and a year are often equivalent. Indonesian uses satu in the same way here.

So:

• selama satu tahun = for one year / for a year

You may also hear:

• selama setahun

This is a very common shorter form, and it means the same thing.

They usually mean the same thing: one year / a year.

• satu tahun = explicitly one year
• setahun = a fused form meaning a year / one year

So these are both natural:

• Perjanjian itu berlaku selama satu tahun.
• Perjanjian itu berlaku selama setahun.

The second one may sound a little more compact and conversational, but both are correct.

Indonesian verbs do not change form for tense the way English verbs do.

So berlaku itself does not tell you whether something is present, past, or future. The time usually comes from:

• context
• time words
• other markers such as sudah, akan, sedang, etc.

By itself, this sentence is most naturally understood as present or general:

• The agreement is valid for one year.

But in the right context, it could also refer to past or future.

Examples:

• Perjanjian itu sudah berlaku selama satu tahun. = The agreement has already been in effect for one year.
• Perjanjian itu akan berlaku selama satu tahun. = The agreement will be valid for one year.

In this sentence, selama is the better and more natural choice because it expresses duration.

• selama satu tahun = for one year

Untuk usually means things like:

• for (for someone / for a purpose)
• to
• in order to

So:

• berlaku selama satu tahun = valid for one year ✅
• berlaku untuk semua karyawan = applies to all employees ✅

But:

• berlaku untuk satu tahun is less natural if you mean duration

So the safest choice here is selama.

It is used in many situations, not just contracts.

Common uses of berlaku include:

• documents: permits, passports, tickets
• rules/laws: whether they apply
• promotions/offers: whether they are valid
• agreements/contracts: whether they are in effect

Examples:

• SIM ini berlaku sampai 2027. = This driver’s license is valid until 2027.
• Diskon ini berlaku hari ini saja. = This discount is valid today only.
• Peraturan baru itu berlaku mulai Senin. = The new regulation takes effect starting Monday.

So it is a very useful word.

They are similar, but not always identical.

• perjanjian = agreement
• kontrak = contract

Perjanjian is a broader word. It can refer to an agreement in general, including formal legal agreements.

Kontrak often sounds more specifically legal, formal, or business-related.

In many real situations, especially legal or business contexts, the two can overlap. But if the English meaning shown to the learner is agreement, then perjanjian is exactly the expected word.

A simple breakdown is:

• Perjanjian itu = noun phrase (subject)
• berlaku = predicate/verb
• selama satu tahun = time-duration phrase

So the pattern is:

Subject + predicate + duration

More literally:

• The agreement
  • is valid / remains in effect
    • for one year

This is a very common and straightforward Indonesian sentence pattern.